Connect with us


Discussion in 'Power Electronics' started by bigkim100, Feb 4, 2020.

Scroll to continue with content
  1. bigkim100


    Apr 17, 2013
    I have a Futaba Battery Pack that is a plastic-wrapped cabal of 8-AA batteries, marked Ni-Cad 9.6V 700Ma.
    I would like a cheap and easy schematic for a charger for this.
    Thanks in advance
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Any NiCd charger will do. Heer is but one example.

    Note that all simple chargers are not good for your batteries in the long term as they offer no protection against overcharging. A better charger will at least include a timer to limiut charging time. Even better it will include an end of charge detetctor (e.g. using dv/dt) to stop charging when the battery is fully charged. See e.g. this kit.
  3. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Ni-Cad batteries, huh? Aren't those the ones that "remember" how much you discharged them, and then stubbornly refuse to accept a full charge again? And, IIRC, don't they also grow internal "whiskers" that short individual cells, playing havoc with attempts to charge series-connected cells in battery packs? Wouldn't you rather like to have some nice, modern, lithium-ion polymer cells instead? Or, if you don't mind a little extra weight, maybe some nice sealed lead-acid (SLA) batteries that are easy to charge and can be kept of a "float" charge for months at a time until needed, perhaps in an emergency, would suit your application. BTW, what are you planning to use those obsolete NiCd batteries to power?

    I have had very good success using Panasonic Eneloop Pro AA cells, BK-3HCCA, which are 2450 mAh, 1.2 V NI-MH (nickel metal hydride) cells to replace NiCd cells. They seem to recharge well with a Panasonic BQ-CC17 four-cell, plug-in "smart" battery charger. Unlike some four-cell chargers which require either two or four cells for charging, this little charger happily accepts one, two, three, or four cells. Each cell is tested and charged individually. If a cell fails initial (or subsequent) testing, a little LED light under that cell starts flashing. Good cells result in a steadily on light until charging is complete, whereupon the light goes off.

    You can charge cells of different ampere-hour capacities with this charger. Beats the pants off my Energizer charger. It will also charge the four AAA Ni-MH cells in my high-intensity "tactical" flashlight. I have never timed how long it takes to charge a nearly dead Ni-MH cell... you aren't really supposed to discharge them to a dead state... but I generally load the charger up with cells before I retire for the night and they are fully charged the next morning. Since the charger shuts off automagically, I never have to worry about overcharging my cells. I think re-chargeable Ni-MH cell chemistry is a more cost-effective alternative to re-chargeable lithium ion chemistry if you don't need the better power-to-weight performance of lithium ion cells. And the Ni-MH chemistry is demonstrably better than the old NiCd chemistry.

    Good luck with your search for a suitable NiCd charger.
  4. Bluejets


    Oct 5, 2014
    Would have to be literally millions of the Plug Pack Futaba Tx/Rx chargers around r/c aircraft flyers you could pick up for a couple of bucks.

    Plus 2 for the Eneloop AA.
    Last edited: Feb 5, 2020
  5. Audioguru


    Sep 24, 2016
    Energizer and Duracell also sell Japanese-made AA size Ni-MH cells that use the Eneloop chemistry that holds a charge for one year.
    The cells are sold pre-charged.
  6. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    I have used both brands, but the Panasonic Eneloop cells seem to charge quicker and last longer, at least for my applications.

    It was the Energizer cells that prompted me to purchase the Energizer 4-cell charger, to charge about eight of them, a few years ago, mainly for flashlight and digital camera use. Then a few years later I bought an Elecraft KX3 low-power (12 watts or less) portable amateur radio transceiver that uses either internal AA cells for portable power, or a cable with a coaxial barrel-plug on one end and a "car cigarette lighter" plug on the other end for "tethered to a bigger battery" portable power. A similar cable can also be wired into a wall-wart, but most of them have inadequate current capability for ten or twelve watts output, although the KX3 can be set to transmit with lower power. Also, unless you are careful in selecting your purchase, the wall-wart switching power supply will overload the KX3 receiver front-end with switching transients... or so I have been told. I haven't actually taken my KX3 out into the boondocks yet, or to the summit of a mountain (a favorite ham activity), "activating" a new Summit On The Air (SOTA) station for a short period of time, but this is type of portable activity is normally conducted using the internal battery, so power supply switching noise is not a problem.

    Unfortunately, Elecraft made NO provision for recharging the AA cells while they are installed in the KX3, so most hams keep a spare set of twelve charged and ready to go. With that in mind, one year at the Dayton Hamvention I bought a boatload of Ni-MH cells from MFJ Enterprises. These turned out to be Chinese imports of poor quality. Some would not charge. Of the remainder that seemed to take a charge, all of them discharged very rapidly when used in the KX3. Same-o, same-o when used in my MFJ antenna analyzer. So the next day I took them back and MFJ cheerfully replaced them with like stock. Sorry, no cash refunds, Charlie!

    Around the corner, (practically) more or less in the next room, were "lower tier" vendors who couldn't or wouldn't pay for premium space on the main arena floor at Hamvention. One of these seemed to be selling Panasonic Eneloop batteries like they were discounted premium pork sausages. After elbowing my way to the front of the crowd to see what all the excitement was about, I decided to buy a few Eneloop AA and AAA cells, along with the Panasonic wall-mounted charger. I have never regretted my purchase, and try to set aside a little money each year to purchase a few more cells, either at a local hamfest or via online order from Amazon Prime.
    Last edited: Feb 6, 2020
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day